The present invention relates to a safeguard arrangement for a plant, and particularly to a safeguard arrangement for a plant for securing the safety of personnel for maintenance when a test with any people being admitted or maintenance is executed.
In a plant such as a thermal power plant, the inspection and maintenance of plant auxiliaries are conducted properly for maintaining sound operations of the plant, and it is indispensable, on the occasion, to secure the safety of the maintenance personnel in terms of both mind and body thereof. A sudden motion of some peripheral apparatus in the course of the maintenance, for instance, frightens the personnel, and also exposes them to serious danger, just causing casualty in some cases, when they work at a height. Such matters as stated above must be avoided without fail.
On the occasion of maintenance of plant auxiliaries, therefore, warning tags for prohibiting operations are usually put on the operation switches of said auxiliaries and the peripheral apparatuses so as to prevent the erroneous operation of said switches by any operator other than the maintenance personnel concerned. Besides, a process control system is known wherein the delivery of a control instruction from a process control unit to a process apparatus is prohibited by operating a switch for maintenance and inspection provided in a process input/output device on the occasion of the maintenance and inspection of the process control system, as described in Japanese Patent Laid-Open No. 91507/1984.
Among the plant auxiliaries, there are units, such as a condenser waterbox, a feed water heater, a coal pulverizer, a fan, a motor and a pump, which have a so-called lid, such as a manhole, a hatch or a cover, which is opened for internal on-the-spot maintenance. In many cases, moreover, a plurality of these auxiliaries are installed in juxtaposition to obtain a prescribed output, and therefore it sometimes happens that a part of the auxiliaries is stopped and subjected to the maintenance while a partial loaded operation is executed. On the occasion of the maintenance of the stopped auxiliary, apparatuses on the entrance and exit sides thereof are closed, a rotary machine is stopped, the inflow of a fluid is checked, and the fluid located inside is discharged, before the maintenance is executed. However, if an apparatus on the entrance or exit side is opened on the rotary machine is driven erroneously on the occasion, a great injury is to be inflicted on the personnel working inside.
In terms of the safeguard regarding such auxiliaries as mentioned above, the method relying on the manual operations of the warning tag for prohibiting operation and the switch for maintenance and inspection according to the above-described prior art can not eliminate the possibility of forgetting to set the warning tag, to operate the switch for maintenance and inspection, or the like, and it can also be imagined that an operation switch is operated erroneously by a person not knowing that a given auxiliary is under maintenance. These failures cause the problem that the maintenance personnel are imperiled by the operation of the auxiliary under maintenance or a related apparatus.